DeMayo died on June 2, 2005[2] in Boston from a heroin overdose.[3] According to people close to him[4], DeMayo's problems started when his wife left him and he returned to Boston after he moved to California with her to train in Gold's Gym. He then was signed to an endorsement contract by sports nutritional supplement company Met-Rx and forced to compete in the 1995 Mr. Olympia against his wishes. He placed 12th and retired shortly afterwards.
DeMayo spent two years in Walpole state prison for shooting at his girlfriend and possession of percodan. Some months before his death he told his friends that he was working at the Gold's Gym on Lansdown Street in Boston, but it was revealed later that he was fired several months earlier due to a substance abuse problem.[4]